jupyter-js-services - how to save notebook - jupyter

Question

I'm trying to use jupyter as a backend for my system and now I play with examples from jupyter-js-api docs.
Using IKernel and INotebookSession I managed to execute simple code and get the response form kernel.
But I can's figure out how to extract the notebook itself. there's nothing like "saveNotebook()" in API. I try to execute session.renameNotebook(), it completes successfully, but no files appear in filesystem (tried different paths like "/tmp/trynote.ipynb" "trynote.ipnb" and so on...).
Here's the code, it is slightly edited example from http://jupyter.org/jupyter-js-services/ page
#!/usr/bin/env node
var jpt = require("jupyter-js-services");
var xr = require("xmlhttprequest");
var ws = require("ws");
global.XMLHttpRequest = xr.XMLHttpRequest;
global.WebSocket = ws;
// start a new session
var options = {
baseUrl: 'http://localhost:8889',
wsUrl: 'ws://localhost:8889',
kernelName: 'python',
notebookPath: 'trynote.ipynb'
};
jpt.startNewSession(options).then((session) => {
// execute and handle replies on the kernel
var future = session.kernel.execute({ code: 'print(5 * 5);' });
future.onDone = (msg) => {
console.log('Future is fulfilled: ');
console.log(msg);
};
future.onIOPub = (msg) => {
console.log("Message in IOPub: ");
console.log(msg);
};
// rename the notebook
session.renameNotebook('trynote2.ipynb').then(() => {
console.log('Notebook renamed to', session.notebookPath);
});
// register a callback for when the session dies
session.sessionDied.connect(() => {
console.log('session died');
});
// kill the session
session.shutdown().then(() => {
console.log('session closed');
});
});
Looking and ContentManager API it seems to work with already existing files, or creating new ones, but its unclear how is it bound to sessions.
More, even simplest try to use "newUntitled" function gives 404 response...
var contents = new jpt.ContentsManager('http://localhost:8889');
// create a new python file
contents.newUntitled("foo", { type: "file", ext: "py" }).then(
(model) => {
console.log(model.path);
}
);
I feel a bit disoriented with all this and would appreciate any explanations.
Thanks..